Projectors flicker when Arduino relay switches fans

Other Hardware General Electronics
1

I’m working on a project where an Arduino Uno controls a 2-channel relay module (5V, opto-isolated, model: Eletrogate 2-channel relay).

Relay channel 1 → 1 fan (AC, 220V)

Relay channel 2 → 2 fans (AC, 220V)

The Arduino is connected to a computer that also drives multiple projectors.

Problem:
Whenever the relay switches the fans on or off, the projectors flicker and sometimes lose HDMI signal, taking a few seconds to recover.

What I’ve tried:

Running fans and projectors on the same electrical circuit → issue persists.

Running fans and projectors on separate circuits → issue persists.

Question:
What could be causing this problem, and what’s the best way to solve it?
Has anyone experienced similar issues with relays switching AC fans and projectors losing signal?

2

Does the same thing happen if the fans are switched manually?
(i.e. the relays and Arduino are taken out of the picture)

Could you please post a diagram showing how everything is wired up and the power sources?

3

Hi, @sandrozw
Welcome to the forum.

If you disconnect the fans but still have the relays operate, does the problem persist?

Can you please post some images of your project?
So we can see your component layout.

Thanks.. Tom.... :smiley: :+1: :coffee: :australia:

2 Likes
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  • Always show us a good schematic of your proposed circuit.
    Show us good images of your ‘actual’ wiring. Give links to components.
5

Thanks for the replies!

@BitSeeker Yes, same thing happens if the fans are switched manually.

@TomGeorge No, if the fans are disconnected and I control the relays the problem doesn't happen.

I don't have pictures or a schematic of my circuit but I can explain here:

  • Computer is connected to three projectors via HDMI cables (high quality 4k protected 10m cables).
  • Relay is wired to an Arduino that's connected to the Computer via USB cable.
  • The energy wires of the fans go through the relay and to a dedicated power source.

Found this image online and it's pretty similar to my Arduino circuit (source):

relay-with-arduino-circuit
relay-with-arduino-circuit1200×628 58.8 KB

The only difference is that I have a 2-channel relay and I'm controlling fans instead of a light bulb.

6

Tom.... :smiley: :+1: :coffee: :australia:

7

Another difference is you do not show the projector and fans 220 VAC connection. Are you using an extension cord that powers all of them?

1 Like
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You may want to place a RC Snubber circuit in series with your load. Just do a basic Google of RC Snubber circuits. Since under no load the problem goes away I would assume your 220V AC fans are an inductive load and therefore suggest an AC Snubber circuit. As to a snubber circuit you can build or just buy.

Ron

9

What does that mean, how are they protected?
Since the problem also occurs when you manually turn on the fans, then you can rule out any problems with the Arduino or relay board.

What kind of fans are they?

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